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Physiology 201 > U2 Lecture 6 > Flashcards

U2 Lecture 6 Flashcards

- Describe the dietary factors that influence bone - Describe the roles of calcitonin and parathyroid hormone in the regulation of blood calcium - describe the vitamin D pathway, and the role of calcitriol in calcium homeostasis - Describe the role of dietary calcium in maintenance of bone mass and know the recommended allowance for calcium intake for young adults - Describe the role of growth hormone and sex hormones in modulating bone mass - Describe the skeletal disorders that arise fro

1
Q

What factors affect bone density?

A

Diet, hormones and exercise

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2
Q

What are the dietary categories that affect bone density?

A

Minerals and Vitamins

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3
Q

What minerals affect bone density?

A

Calcium and phosphorus (also magnesium, fluoride, and manganese)

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4
Q

What vitamins affect bone density?

A

Vitamin A, C, D, K B12

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5
Q

What does vitamin A do?

A

Stimulates activity of osetoblasts

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6
Q

What does vitamin C do?

A

Needed for collagen synthesis

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7
Q

What does vitamin D do?

A

Stimulates calcium absorption

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8
Q

What does vitamin K, B12 do?

A

Needed for synthesis of bone proteins

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9
Q

Define calcium homeostasis

A

Maintaining adequate calcium levels in the body

Normal Range: 8.5 - 11 mg/dL

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10
Q

Why is calcium homeostasis important?

A

Membrane excitability, blood clotting and intracellular activity (second messenger

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11
Q

How does the body control calcium entry and exit from blood?

A

Through level of storage in bone, through level of kidney excretion, and through intestinal absorption levels

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12
Q

Extracellular fluid Ca2+ represents how much of total body calcium?

A

1% but it is highly regulated

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13
Q

What hormones are involved in calcium homeostasis?

A

Calcitonin, Parathyroid hormone, and calcitriol (Vitamin D)

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14
Q

What type of molecule is Calcitonin?

A

Polar with H bonding

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15
Q

Calcitonin stimulus

A

High blood calcium

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16
Q

Calcitonin source

A

Thyroid gland (parafollicular cells “C cells”)

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17
Q

Calcitonin target tissues

A

Bone, kidney, and intestine

18
Q

Calcitonin actions

A

Goal: DECREASE blood Ca2+ concentration

  • inhibits osetoclast activity (decreased bone resorption)
  • increases excretion of calcium at kidney
  • inhibits intestinal absorption of calcium
19
Q

Calcitonin end result

A

DECREASE in blood calcium concentration

20
Q

What type of molecule is the parathyroid hormone?

A

Polar

21
Q

Parathyroid hormone stimulus

A

Low blood calcium

22
Q

Parathyroid hormone source

A

Parathyroid gland

23
Q

Parathyroid hormone target tissues

A

Bone, kidney, intestine

24
Q

Parathyroid hormone actions

A

Goal: INCREASE blood Ca2+ concentration

  • stimulates osteoclast activity (increased bone resorption)
  • Decreases excretion of calcium at kidney
  • stimulates intestinal absorption of calcium and promotes calcitriol (active vit. D) action
25
Q

Parathyroid hormone end result

A

INCREASE blood calcium concentration

26
Q

Define negative feedback

A

When levels inside the body get too extreme, the body counter acts them and does the opposite

27
Q

Negative feedback regulation of blood Ca2+ concentration

A

When blood calcium levels get too high, calcitonin is released

When blood calcium levels get too low, Parathyroid hormone is released

28
Q

What type of molecule is Calcitriol

A

Calcitriol is active vitamin D

  • Very non-polar
  • hydrophobic
  • fat soluble
  • steroid hormone- derived from cholesterol (lipophillic / hydrophobic)
29
Q

Vitamin D pathway

A
  • Starts in 2 places: skin or intestine
  • Skin - light hits vit. D in skin then turns it into vit. D3. Then goes through blood to liver
  • Intestine - get dietary vit. D3 from fish oil, egg yolk, milk and goes straight to liver through blood
  • In liver, all vit. D3 turns into 25-hydroxycholecalciferol
  • goes through blood again to kidney where the active form of vit. D is (calcitriol), PTH will increase levels of Ca2+ if there’s low blood calcium
30
Q

Calcitriol stimulates

A

It stimulates osetoclast activity (bone resorption)

31
Q

Calcitriol actions

A
  • Decreases calcium excretion at the kidney

- Increases calcium absorption at the intestine (works well with PTH to stimulate absorption)

32
Q

Calcitriol end result

A

INCREASE blood calcium

33
Q

What is the recommended Ca2+ intake for young adults?

A

1000 mg to avoid bone loss

34
Q

What hormones act on osteoclasts?

A

Calcitonin and parathyroid hormone

35
Q

What hormones act on osteoblasts?

A

growth hormone (sometotropin) and estrogen/ testosterone

36
Q

Growth Hormone (GH or Somatotropin)

A
  • stimulates cell growth and protein synthesis (collagen)
  • stimulates formation of insulin like growth factors (IGF’s) -> stimulates osteoblast activity -> stimulates bone formation
37
Q

Skeletal disorders associated with GH

A

Pituitary dwarfism, pituitary gigantism, acromegaly

38
Q

Pituitary dwarfism

A

decrease in GH, slow epiphyseal growth

39
Q

Pituitary gigantism

A

increase in GH, high epiphyseal growth

40
Q

Acromegaly

A

Increase in GH after puberty, thickening of bone

41
Q

Estrogen and Testosterone

A
  • Both stimulate osteoblast activity -> stimulate bone formation
  • Levels increase at puberty: bone growth/ spurts, eventually cause closure of epiphyseal plates bc osteoblast/osteoclast activity is greater than chondrocyte activity
  • levels decrease with old age

Physiology 201 (38 decks)

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